Immediate Patches for 4E

1) Change the XP system. Right now 4E rewards combat 80% and quests 20%. In 1E, you got rewarded treasure (quest) 80%, combat 20%. That means that in 4E, combat is the preferred and best solution to almost every problem. If the players are clever and manage to avoid or attrit a combat encounter, the GM often feels guilty handing out full XP. Because in 4E, XP is linked to treasure, players basically get zero reward for avoiding combat. Players will not seek out creative (non-violent) solutions unless they are rewarded for doing so. This turns most adventures into a room-to-room clearing exercise where the players wipe out everything in the dungeon, with many of the "easy" encounters not really posing any threat; they just provide XP and sap resources.

2) A Focused Campaign. 4E is built out of the box to support a very, very wide idea of fantasy gaming. There's multiple planes of existence, skills to handle everything from mountaineering to lying to the Duke to dungeon crawling, and a broad variety of classes. It isn't as bad as other editions, but at this point I would prefer to look at a smaller topic in greater detail (deep and narrow over broad and shallow). Also, with the characters potentially hailing from very different places mechanically, the only thing they have in common is tactical combat. So, what will they do? Tactical Combat, every time. The fix, I think, is working with the players to create a cohesive party and themed game. Maybe we're playing "Knights and Knaves" and players are restricted to the Martial Power Source. Perhaps the players are in a Sorcerer's Guild and are all Arcane Power Source. Maybe all characters must be Fey creatures, or part of a thieve's guild, or something. This may entail granting carrots (characters of X trait gain some sort of benefit, free multiclass feats) or sticks (outright bans of certain material).

3) Morality. D&D has always been designed to mechanically support "low" fantasy, that is, Swords & Sorcery. See my post on "survival" for more on this line of thought. I would either implement a morally gray Swords & Sorcery "sell swords for hire" campaign world, or add some sort of mechanic (morality, honor/shame, virtue/vice, something) to reward and encourage "heroic" or desired behavior.

4) Out of Combat. Non-combat activities need some serious thought. If you want people to do something other than Tactical Combat it has to be interesting. Tweaking of the skill challenge system is the most obvious route.